While looking for ways to query specific information about a range of pages in windows I came across two solutions that were used commonly. However these two alternatives seem to return overlapping information.
VirtualQueryEx
Found on MSDN we see that it takes the parameters hProcess, lpAddress, lpBuffer and dwLength to query information for that range of pages. It returns this struct which tells us something about page state, protection and type. Oh well, so a good choice for querying page information right? But wait there is more!
QueryVirtualMemoryInformation
Also found on MSDN and does nearly the same thing. The difference is that it uses a DUMMYSTRUCTNAME and returns a memory structure that overlaps quite perfectly with the struct returned by VirtualQueryEx.
It seems like this could be an oversight and it doesn't matter which one to use. Maybe MS themselves don't even know why there are two overlapping variants inside a single OS. But for someone that does know: What's the difference here?
VirtualQuery and VirtualQueryEx have existed since forever (NT v3.51).
QueryVirtualMemoryInformation is much newer (10 1607) and adds the information class parameter often seen in the NT API. This allows for future expansion. There is currently only one documented class value and the returned information is pretty similar to VirtualQueryEx but not exactly the same (BaseAddress, CommitSize etc).
DUMMYSTRUCTNAME is a compiler thing related to members without a name and has nothing to do with the actual data returned.